Meat and Dairy Industry's Attempt to Change How We Measure Methane Emissions Would Let Polluters Off the Hook

By Tom Higgs and Dmitry Yumashev et.al

Lobbyists from major polluting industries were out in force at the recent UN climate summit, COP28. Groups representing the livestock industry, which is responsible for around 32% of global methane emissions, want to increase their use of a new way of measuring these emissions that lets high polluters evade their responsibility to make big emissions cuts.

Not all greenhouse gases are created equal. Carbon dioxide, the biggest driver of global warming, will build up in the atmosphere when continuously emitted, warming the Earth for centuries to come. Methane, the second-biggest driver, is more effective at trapping heat in the atmosphere, but most of it naturally breaks down a couple of decades after being emitted. The damage from a single burst of methane is intense but limited.

When emitted continuously, the additional heating caused by methane will remain constant after the initial rise. But ramping down methane emissions rapidly would have a swift and positive effect on global heating.

To understand the climate effects of different activities and develop pathways consistent with limiting warming to 1.5°C, it is often useful to combine the effects of different gases into a single metric. GWP100—a gas's global warming potential over 100 years—has become the dominant metric and has been adopted as a standard by the UN.

However, GWP100 fails to capture the different ways methane and carbon dioxide behave in the atmosphere. It also masks the more intense short-term effect of methane compared to carbon dioxide. GWP100 simply measures the mass of each gas released into the atmosphere and considers 1kg of methane as equivalent to 28kg of carbon dioxide in terms of its climate impact.

So in 2016, scientists at the University of Oxford proposed a new method for modeling methane and carbon dioxide together called GWP*. This model is more complex and takes account of both the level of emissions and the changes in emissions compared to a recent baseline year.

But, because it relies on changes since the baseline year, GWP* can allow a historically high emitter to look good by making minor cuts to their emissions.

When used at any level other than globally, the use of the baseline year bakes in the current unequal distribution of responsibility for methane emissions and simply projects this situation into the future. The usual baseline year is 20 years before today, and so would imply rich countries' retaining their high share of global methane emissions, mainly due to their high meat and dairy consumption.